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- Akenine-Möller, Tomas, et al.
(författare)
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Texture Level of Detail Strategies for Real-Time Ray Tracing
- 2019
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Ingår i: Ray Tracing Gems : High-Quality and Real-Time Rendering with DXR and Other APIs - High-Quality and Real-Time Rendering with DXR and Other APIs. - Berkeley, CA : Apress. - 9781484244265 - 9781484244272 ; , s. 321-345
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Bokkapitel (refereegranskat)abstract
- Unlike rasterization, where one can rely on pixel quad partial derivatives, an alternative approach must be taken for filtered texturing during ray tracing. We describe two methods for computing texture level of detail for ray tracing. The first approach uses ray differentials, which is a general solution that gives high-quality results. It is rather expensive in terms of computations and ray storage, however. The second method builds on ray cone tracing and uses a single trilinear lookup, a small amount of ray storage, and fewer computations than ray differentials. We explain how ray differentials can be implemented within DirectX Raytracing (DXR) and how to combine them with a G-buffer pass for primary visibility. We present a new method to compute barycentric differentials. In addition, we give previously unpublished details about ray cones and provide a thorough comparison with bilinearly filtered mip level 0, which we consider as a base method.
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- Andersson, Arne, et al.
(författare)
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A New Analysis of Combinatorial vs Simultaneous Auctions: Revenue and Efficiency
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We address the fundamental issue of revenue and efficiency in the combinatorial and simultaneous auction using a novel approach. Specifically, upper and lower bounds are constructed for the first-price sealed-bid setting of these two auctions. The question of revenue is important yet very few results can be found in the literature. Only for very small instances with 2 items have comparisons been made. Krishna et. al. find that allowing combinatorial bids result in lower revenue compared to a second price simultaneous auction. We formulate a lower bound on the first-price combinatorial auction and an upper bound on the first-price simultaneous auction for larger problems with several items and many bidders, in a model where bidders have synergies from winning a specific set of items. We show that the combinatorial auction is revenue superior to the simultaneous auction for a specific instance in pure symmetric equilibrium and give two generalized upper bounds on revenue for the simultaneous auction.
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- Andersson, Arne, et al.
(författare)
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A New Analysis of Revenue in the Combinatorial and Simultaneous Auction
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We prove that in many cases, a first-price sealed-bid combinatorial auction gives higher expected revenue than a sealed-bid simultaneous auction. This is the first theoretical evidence that combinatorial auctions indeed generate higher revenue, which has been a common belief for decades.We use a model with many bidders and items, where bidders are of two types: (i) single-bidders interested in only one item and (ii) synergy-bidders, each interested in one random combination of items. We provide an upper bound on the expected revenue for simultaneous auctions and a lower bound on combinatorial auctions. Our bounds are parameterized on the number of bidders and items, combination size, and synergy.We derive an asymptotic result, proving that as the number of bidders approach infinity, expected revenue of the combinatorial auction will be higher than that of the simultaneous auction. We also provide concrete examples where the combinatorial auction is revenue-superior.
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- Andersson, Bo, et al.
(författare)
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Structure Functions and general final state properties in the linked dipole chain model
- 1996
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Ingår i: Zeitschrift für Physik C Particles and Fields. - : Springer Science and Business Media LLC. - 0170-9739 .- 1431-5858. ; 71:4, s. 613-624
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Tidskriftsartikel (refereegranskat)abstract
- We have in an earlier paper, [1], presented a generalization, the Linked Dipole Chain Model LDC, of the model developed by Ciafaloni-Catani-Fiorani-Marchesini, [2], to decribe the structure functions and the states in Deep Inelastic Scattering events. In this paper we would like to present an investigation of a set of general features of the LDC Model, viz the behaviour of the structure functions (we will show how the result interpolates in a precise way in between the well-known DGLAP and BFKL approaches), the average bremsstrahlung emission in the states and finally a partitioning of the structure functions into three different channels: the ''ordinary'' parton-probe events, where all bremsstrahlung emissions are below the probe Q(2), the boson-gluon fusion events where the last splitting of the par ton chains contain transverse momentum above Q(2), and the resolved Rutherford scattering events between the probe and the hadron (where the largest transverse momentum occur somewhere along the emission lines away from the ends).
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- Andersson, Jim, et al.
(författare)
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Co-gasification of black liquor and pyrolysis oil : Evaluation of blend ratios and methanol production capacities
- 2016
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 110, s. 240-248
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Tidskriftsartikel (refereegranskat)abstract
- The main aim of this study is to investigate integrated methanol production via co-gasification of black liquor (BL) and pyrolysis oil (PO), at Swedish pulp mills. The objectives are to evaluate techno-economically different blends ratios for different pulp mill capacities. Furthermore, the future methanol production potential in Sweden and overall system consequences of large-scale implementation of PO/BL co-gasification are also assessed.It is concluded that gasification of pure BL and PO/BL blends up to 50% results in significantly lower production costs than what can be achieved by gasification of unblended PO. Co-gasification with 20–50% oil addition would be the most advantageous solution based on IRR for integrated biofuel plants in small pulp mills (200 kADt/y), whilst pure black liquor gasification (BLG) will be the most advantageous alternative for larger pulp mills. For pulp mill sizes between 300 and 600 kADt/y, it is also concluded that a feasible methanol production can be achieved at a methanol market price below 100 €/MW h, for production capacities ranging between 0.9 and 1.6 TW h/y for pure BLG, and between 1.2 and 6.5 TW h/y for PO/BL co-gasification. This study also shows that by introducing PO/BL co-gasification, fewer pulp mills would need to be converted to biofuel plants than with pure BLG, to meet a certain biofuel demand for a region. Due to the technical as well as organizational complexity of the integration this may prove beneficial, and could also potentially lower the total investment requirement to meet the total biofuel demand in the system. The main conclusion is that PO/BL co-gasification is a technically and economically attractive production route for production biomethanol.
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